The application of the powerful tool molecular biology has made it possible to ask questions not only about hormone production and action but also to characterize many of the receptor molecules that initiate responses to the hormones. We are beginning to understand how cells may regulate the expression of genes and how hormones intervene in regulatory processes to adjust the expression of individual genes. In addition, great strides have been made in understanding how individual cells talk to each other through locally released factors to coordinate growth, differentiation, secretion, and other responses within a tissue. In this review I (1) focus on developmental aspects of the pituitary gland, (2) focus on the different components of the growth hormone axis and (3) examine the different altered genes and their related growth factors and/or regulatory systems that play an important physiological and pathophysiological role in growth. Further, as we have already entered the 'post-genomic' area, in which not only a defect at the molecular level becomes important but also its functional impact at the cellular level, I concentrate in the last part on some of the most important aspects of cell biology and secretion.